[py3k] replace 'unicode' with 'cubicweb._'

views.py

@@ -6,7 +6,10 @@
 """
 __docformat__ = "restructuredtext en"
 
-_ = unicode
+try:
+    from cubicweb import _
+except ImportError:
+    _ = unicode
 
 from logilab.mtconverter import xml_escape